An example of a device that can generate a signal with a high dynamic range is a microphone. These can detect very quiet sounds (such as whispering) through to very loud sounds (such as a concert or an aircraft taking off) without distortion.
In some cases, it can be difficult or impossible to handle this high dynamic range signal. For example, in a mobile phone application, the digital channel coupling the microphone to the baseband circuitry is limited in terms of the dynamic range it can handle. Furthermore, the characteristics of the digital channel are specified by a standard, and so it is impossible to enhance these characteristics. Thus, any attempt to handle a higher dynamic range must be compatible with this digital channel and with existing baseband circuitry.
Existing techniques for improving the dynamic range of a signal make use of signal compression (e.g. companding) techniques or of time varying gain controls (e.g. automatic gain control). However, these affect the linearity of the signal and are incompatible with various signal processing algorithms, such as noise reduction and echo cancellation algorithms.